Indirect printing apparatus employing sacrificial coating on intermediate transfer member

ABSTRACT

A sacrificial coating composition for an image transfer member in an aqueous ink imaging system. The sacrificial coating composition includes a latex having polymer particles dispersed in a continuous liquid phase; at least one hygroscopic material; at least one surfactant; and water.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a divisional of U.S. patent application Ser. No.14/288,633 filed May 28, 2014, the disclosure of which is herebyincorporated herein by reference in its entirety.

FIELD OF THE DISCLOSURE

This disclosure relates generally to indirect inkjet printers, and inparticular, to a sacrificial coating employed on an intermediatetransfer member of an inkjet printer.

BACKGROUND

In aqueous ink indirect printing, an aqueous ink is jetted on to anintermediate imaging surface, which can be in the form of a blanket. Theink is partially dried on the blanket prior to transfixing the image toa media substrate, such as a sheet of paper. To ensure excellent printquality it is desirable that the ink drops jetted onto the blanketspread and become well-coalesced prior to drying. Otherwise, the inkimages appear grainy and have deletions. Lack of spreading can alsocause missing or failed inkjets in the printheads to produce streaks inthe ink image. Spreading of aqueous ink is facilitated by materialshaving a high energy surface.

However, in order to facilitate transfer of the ink image from theblanket to the media substrate after the ink is dried on theintermediate imaging surface, a blanket having a surface with arelatively low surface energy is preferred. Rather than providing thedesired spreading of ink, low surface energy materials tend to promote“beading” of individual ink drops on the image receiving surface.

Thus, an optimum blanket for an indirect image transfer process musttackle both the challenges of wet image quality, including desiredspreading and coalescing of the wet ink; and the image transfer of thedried ink. The first challenge—wet image quality—prefers a high surfaceenergy blanket that causes the aqueous ink to spread and wet thesurface. The second challenge—image transfer—prefers a low surfaceenergy blanket so that the ink, once partially dried, has minimalattraction to the blanket surface and can be transferred to the mediasubstrate.

Various approaches have been investigated to provide a solution thatbalances the above challenges. These approaches include blanket materialselection, ink design and auxiliary fluid methods. With respect tomaterial selection, materials that are known to provide optimum releaseproperties include the classes of silicone, fluorosilicone,fluoropolymer such as TEFLON or VITON, and certain hybrid materials.These materials have low surface energy, but provide poor wetting.Alternatively, polyurethane and polyimide have been used to improvewetting, but at the cost of ink release properties.

Identifying and developing new techniques and/or materials that improvewet image quality and/or image transfer in aqueous ink indirect printingwould be considered a welcome advance in the art.

SUMMARY

An embodiment of the present disclosure is directed to a sacrificialcoating composition for an image transfer member in an aqueous inkimaging system. The sacrificial coating composition comprises a latexcomprising polymer particles dispersed in a continuous liquid phase; atleast one hygroscopic material; at least one surfactant; and water.

Another embodiment of the present disclosure is directed to an indirectprinting apparatus. The indirect printing apparatus comprises anintermediate transfer member. A sacrificial coating is made bydepositing and drying a sacrificial coating composition on theintermediate transfer member. The sacrificial coating compositioncomprises a latex comprising polymer particles dispersed in a continuousliquid phase; at least one hygroscopic material; at least onesurfactant; and water. The indirect printing apparatus further comprisesa coating mechanism for forming the sacrificial coating onto theintermediate transfer member and a drying station for drying thesacrificial coating. At least one ink jet nozzle is positioned proximatethe intermediate transfer member and configured for jetting ink dropletsonto the sacrificial coating formed on the intermediate transfer member.An ink processing station is configured to at least partially dry theink on the sacrificial coating formed on the intermediate transfermember. The indirect printing apparatus also includes a substratetransfer mechanism for moving a substrate into contact with theintermediate transfer member.

Yet another embodiment of the present disclosure is directed to anindirect printing process. The process comprises providing an inkcomposition to an inkjet printing apparatus comprising an intermediatetransfer member. A sacrificial coating composition is deposited anddried on the intermediate transfer member to form a sacrificial coating.The sacrificial coating composition comprises a latex comprising polymerparticles dispersed in a continuous liquid phase; at least onehygroscopic material; at least one surfactant; and water. Droplets ofink are ejected in an imagewise pattern onto the sacrificial coating.The ink is at least partially dried to form a substantially dry inkpattern on the intermediate transfer member. Both the substantially dryink pattern and the sacrificial coating are transferred from theintermediate transfer member to a final substrate.

The sacrificial coating compositions of the present disclosure canprovide one or more of the following advantages: coatings having goodwettability on, for example a fluorinated polymer substrate, coatingshaving good ink wetting, good ink spreading, good film uniformity,tunable ink wettability, good ink pinning, image transfer membercoatings exhibiting improved wet image quality and/or improved imagetransfer with aqueous inks, improved physical robustness or increasedshelf life and/or functions as a robust overcoat yielding prints thatare mechanically robust and exhibit long life, good scratch resistance,good water fastness and/or are not susceptible to biodegradation.

It is to be understood that both the foregoing general description andthe following detailed description are exemplary and explanatory onlyand are not restrictive of the present teachings, as claimed.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated in and constitute apart of this specification, illustrate embodiments of the presentteachings and together with the description, serve to explain theprinciples of the present teachings.

FIG. 1 is a schematic drawing of an aqueous indirect inkjet printer thatprints sheet media, according to an embodiment of the presentdisclosure.

FIG. 2 is a schematic drawing of a surface maintenance unit that appliesa sacrificial coating to a surface of an intermediate transfer member inan inkjet printer, according to an embodiment of the present disclosure.

FIG. 3 is a block diagram of a process for printed images in an indirectinkjet printer that uses aqueous inks, according to an embodiment of thepresent disclosure.

FIG. 4A is a side view of a sacrificial coating that is formed on thesurface of an intermediate transfer member in an inkjet printer,according to an embodiment of the present disclosure.

FIG. 4B is a side view of dried sacrificial coating on the surface ofthe intermediate transfer member after a dryer removes a portion of aliquid carrier in the sacrificial coating, according to an embodiment ofthe present disclosure.

FIG. 4C is a side view of a portion of an aqueous ink image that isformed on the dried sacrificial coating on the surface of theintermediate transfer member, according to an embodiment of the presentdisclosure.

FIG. 4D is a side view of a portion of the aqueous ink image that isformed on the dried sacrificial coating after a dryer in the printerremoves a portion of the water in the aqueous ink, according to anembodiment of the present disclosure.

FIG. 4E is a side view of a print medium that receives the aqueous inkimage and a portion of the dried layer of the sacrificial coating aftera transfix operation in the inkjet printer, according to an embodimentof the present disclosure.

FIGS. 5, 6 and 7 show results of film forming evaluations for examplesacrificial coating compositions of the present disclosure.

FIG. 8 shows comparison of ink droplets on various surfaces, asdescribed in the examples of the present disclosure.

FIGS. 9-11 show image transfer test results, as described in theexamples of the present disclosure

It should be noted that some details of the figure have been simplifiedand are drawn to facilitate understanding of the embodiments rather thanto maintain strict structural accuracy, detail, and scale.

DESCRIPTION OF THE EMBODIMENTS

Reference will now be made in detail to embodiments of the presentteachings, examples of which are illustrated in the accompanyingdrawings. In the drawings, like reference numerals have been usedthroughout to designate identical elements. In the followingdescription, reference is made to the accompanying drawings that forms apart thereof, and in which is shown by way of illustration specificexemplary embodiments in which the present teachings may be practiced.The following description is, therefore, merely exemplary.

As used herein, the terms “printer,” “printing device,” or “imagingdevice” generally refer to a device that produces an image on printmedia with aqueous ink and may encompass any such apparatus, such as adigital copier, bookmaking machine, facsimile machine, multi-functionmachine, or the like, which generates printed images for any purpose.Image data generally include information in electronic form which arerendered and used to operate the inkjet ejectors to form an ink image onthe print media. These data can include text, graphics, pictures, andthe like. The operation of producing images with colorants on printmedia, for example, graphics, text, photographs, and the like, isgenerally referred to herein as printing or marking. Aqueous inkjetprinters use inks that have a high percentage of water relative to theamount of colorant and/or solvent in the ink.

The term “printhead” as used herein refers to a component in the printerthat is configured with inkjet ejectors to eject ink drops onto an imagereceiving surface. A typical printhead includes a plurality of inkjetejectors that eject ink drops of one or more ink colors onto the imagereceiving surface in response to firing signals that operate actuatorsin the inkjet ejectors. The inkjets are arranged in an array of one ormore rows and columns. In some embodiments, the inkjets are arranged instaggered diagonal rows across a face of the printhead. Various printerembodiments include one or more printheads that form ink images on animage receiving surface. Some printer embodiments include a plurality ofprintheads arranged in a print zone. An image receiving surface, such asan intermediate imaging surface, moves past the printheads in a processdirection through the print zone. The inkjets in the printheads ejectink drops in rows in a cross-process direction, which is perpendicularto the process direction across the image receiving surface.

As used in this document, the term “aqueous ink” includes liquid inks inwhich colorant is in a solution, suspension or dispersion with a liquidsolvent that includes water and/or one or more liquid solvents. Theterms “liquid solvent” or more simply “solvent” are used broadly toinclude compounds that may dissolve colorants into a solution, or thatmay be a liquid that holds particles of colorant in a suspension ordispersion without dissolving the colorant.

As used herein, the term “hydrophilic” refers to any composition orcompound that attracts water molecules or other solvents used in aqueousink.

As used herein, a reference to a dried layer or dried coating refers toan arrangement of a sacrificial coating after all or a substantialportion of the liquid carrier has been removed from the compositionthrough a drying process.

An embodiment of the present disclosure is directed to a liquidsacrificial coating composition for an image transfer member in anaqueous ink imaging system. The sacrificial coating compositioncomprises (a) a latex comprising polymer particles dispersed in acontinuous liquid phase, (b) at least one hygroscopic material, (c) atleast one surfactant and (d) water.

In an embodiment, the latex can be a colloidal suspension of polymerparticles having a liquid continuous phase comprising water as a majorcomponent, such as in an amount of 50%, 70%, 80% or more by weightrelative to the weight of the continuous phase. Alternatively, any othersuitable liquid carrier can be employed as the continuous phase.

Any suitable polymer particles can be employed. The polymer particlescomprise one or more repeating polymeric units. The polymeric units aremade, for example, from monomers selected from the group consisting ofacrylic acid, acrylates such as alkyl acrylates, examples of whichinclude methyl acrylate, ethyl acrylate, n-butyl acrylate, isobutylacrylate, dodecyl acrylate, n-octyl acrylate, lauryl acrylate, tridecylacrylate and 2-ethylhexyl acrylate, 2-chloroethyl acrylate, β-carboxyethyl acrylate (β-CEA), phenyl acrylate and methyl alphachloroacrylate;methacrylic acid, methacrylates such as methyl methacrylate, ethylmethacrylate, N-butyl methacrylate, lauryl methacrylate, tridecylmethacrylate, 2-ethylhexyl methacrylate and butyl methacrylate; dienessuch as butadiene and isoprene; aliphatic nitriles such asmethacrylonitrile and acrylonitrile; vinyl ethers such as vinyl methylether, vinyl isobutyl ether and vinyl ethyl ether; vinyl esters such asvinyl acetate, vinyl propionate, vinyl benzoate and vinyl butyrate;vinyl ketones such as vinyl methyl ketone, vinyl hexyl ketone and methylisopropenyl ketone; vinylidene halides such as vinylidene chloride andvinylidene chlorofluoride; vinyl substituted heterocyclic amines such asN-vinyl indole, N-vinyl pyrrolidene, vinylpyridine,vinyl-N-methylpyridinium chloride and N-vinyl pyrrolidone; acrylamide;methacrylamide; vinyl substituted aromatic hydrocarbons such as vinylnaphthalene, styrene and p-chlorostyrene; vinyl halides such as vinylchloride, vinyl bromide and vinyl fluoride; alkenes such as ethylene,propylene, butylene and isobutylene, and mixtures thereof. In anembodiment, the latex comprises polymer particles comprising astyrene/n-butyl acrylate/methacrylic acid terpolymer. In an embodiment,the latex comprises polymer particles comprising acrylic resins, such asthose made from at least one monomer selected from the group consistingof methyl acrylate, ethyl acrylate, butyl acrylate, methacrylic acid andacrylic acid. In an embodiment, the polymer particles comprise apolyvinyl acetate copolymer.

The monomers and amounts of monomers employed to make the latex can beadjusted to provide desired properties for the transfix process. Forinstance, acrylic latex and/or styrene n-butyl acrylate latex can bemade with different methacrylic acid (MAA) loadings to alter theproperties of the latex. In one example, different methacrylic acidloadings were employed for different styrene to n-butyl acrylate ratiosto provide very different glass transition temperatures and softeningpoints. An example of loading of methacrylic acid relative to styreneand n-butyl acrylate to make the latex ranges from about 2 to about 20wt %, relative to the total weight of the methacrylic acid, styrene andn-butyl acrylate monomers.

The latex can have any suitable solids content. Examples of suitablesolids content include ranges from about 5% to about 70% by weight, suchas about 10% to about 50% by weight, or about 20% to about 40% byweight, relative to the total weight of the liquid sacrificial coatingcomposition.

The polymer of the latex can have any suitable weight average molecularweight. Examples of suitable weight average molecular weight, Mw,detected by gel permeation chromatography (GPC) range from about 3,000to 300,000, or about 10,000 to about 100,000, or about 25,000 to about75,000. Examples of suitable number average molecular weight, Mn, rangefrom about 1,000 to about 100,000, such as about 2,000 to 50,000, orabout 5,000 to about 15,000.

Latex properties can be adjusted to provide any desired propertiessuitable for the aqueous transfix printing process. For example, theglass transition temperatures, Tg, of the polymer in the latex can rangefrom about −45° C. to about 100° C., such as about −35° C. to 85° C., orabout −15° C. to about 55° C. In an example, the viscosity of the latexis from about 3 cps to 800 cps such as about 5 cps to 500 cps, or about10 cps to 200 cps at 25° C. In an example, the pH of the latex rangesfrom about 1.5 to about 12, such as about 3 to about 10. In an example,the softening point of the polymer in the latex ranges from about 60° C.to about 200° C., such as about 100° C. to about 170° C., or about 120°C. to about 160° C.

In an example, the D50 particle size of the polymer particle in latexranges from about 20 to about 300 nm, such as about 50 nm to about 200nm, such as about 100 nm to about 150 nm; and the particle sizedistribution ranges from about 5 to about 50 nm. The gel content(insoluble portion in toluene) in the latex ranges, for example, from 0to about 20.0%

The chemical structure of the latex containing coating can be tailoredto fine-tune the wettability and release characteristics of thesacrificial coating from the underlying ITM surface. This can beaccomplished by employing one or more hygroscopic materials and one ormore surfactants in the sacrificial coating composition.

Any suitable hygroscopic material (also referred to herein as ahumectant) can be employed. In addition to potentially modifying thesurface characteristics of the coating, the hygroscopic material canfunction as a plasticizer. In an embodiment, the at least onehygroscopic material is selected from the group consisting of glycerol,sorbitol, vinyl alcohol such as ethylene vinyl alcohol, propyleneglycol, hexylene glycol, butylene glycol, xylitol, maltito, polymericpolyols such as polydextrose, glyceryl triacetate, urea andalpha-hydroxy acids (AHA's). A single hydroscopic material or aplurality of hygroscopic materials can be employed.

Any suitable surfactants can be employed. In an embodiment, the at leastone surfactant is selected from the group consisting of an anionicsurfactant, a nonionic surfactant, a siloxane surfactant and afluorosurfactant. In an embodiment, a nonionic surfactant having an HLBvalue ranging from about 4 to about 14 can be employed. A singlesurfactant can be used. Alternatively, multiple surfactants, such astwo, three or more surfactants, can be used. In an embodiment, thesurfactant is a blend of at least 2 species of non-ionic surfactant, onewith a low HLB value ranging from 4 to 8 and a second with a high HLBvalue ranging from 9 to 14.

Examples of suitable surfactants include anionic surfactants (such assodium lauryl sulfate (SLS), Dextrol OC-40, Strodex PK 90, ammoniumlauryl sulfate, potassium lauryl sulfate, sodium myreth sulfate andsodium dioctyl sulfosuccinate series), non ionic surfactants (such assulfynol 104 series, sulfynol 400 series, dynol 604, dynol 810,envirogem 360, secondaryl alcohol ethoxylate series such as Tergitol15-s-7, tergitol 15-s-9, TMN-6, TMN-100x and tergitol NP-9, Triton X-100etc.) and cationic surfactants (such as Chemguard S-106A, ChemguardS-208M, Chemguard S-216M. Some fluorinated or silicone surfactants canbe used in systems such as PolyFox TMPF-136A, 156A, 151N ChemguardS-761p, S-764p Silsurf A008, Siltec C-408, BYK 345, 346, 347, 348 and349. Polyether siloxanne copolymer TEGO Wet-260, 270 500 etc. Someamphoteric fluorinated surfactants can also be used such as alkylbetaine fluorosurfactant or alkyl amine oxide fluorosurfactant such asChemguard S-500 and Chemguard S-111. The amount of surfactant is fromabout 0.01 weight percent of the sacrificial coating to about 2.0 weightpercent of the sacrificial coating.

The ingredients of the sacrificial coating can be mixed in any suitablemanner to form a composition that can be coated onto the intermediatetransfer member. The ingredients can be mixed in any suitable amounts.For example, the latex can be added in an amount of from about 0.5 toabout 30, or from about 2 to about 20, or from about 5 to about 10weight percent based upon the total weight of the coating mixture. Thesurfactants can be present in an amount of from about 0.01 to about 2,or from about 0.1 to about 1.5, or from about 0.5 to about 1 weightpercent, based upon the total weight of the coating mixture. Thehygroscopic material can be present in an amount of from about 0.5 toabout 10, or from about 2 to about 8, or from about 3 to about 5 weightpercent, based upon the total weight of the coating mixture.

As will be discussed in greater detail below, the sacrificial coatingcomposition can be applied to an intermediate transfer member (“ITM”),where it dries to form a solid film. The coating can have a highersurface energy and/or be more hydrophilic than the base ITM, which isusually a low surface energy material, such as, for example, apolysiloxane, such as polydimethylsiloxane or other silicone rubbermaterial, fluorosilicone, TEFLON, or combinations thereof.

In embodiments, the sacrificial coating can first be applied or disposedas a wet coating on the intermediate transfer member. A drying or curingprocess can then be employed. In embodiments, the wet coating can beheated at an appropriate temperature for the drying and curing,depending on the material or process used. For example, the wet coatingcan be heated to a temperature ranging from about 30° C. to about 120°C. for about 0.01 to about 100 seconds or from about 0.1 second to about60 seconds. In embodiments, after the drying and curing process, thesacrificial coating can have a thickness ranging from about 0.02micrometer to about 10 micrometers, or from about 0.02 micrometer toabout 5 micrometers, or from about 0.05 micrometer to about 1micrometers.

The sacrificial coating can be applied to the intermediate transfixmember by any suitable method including, but not limited to spraycoating, spin coating, flow coating and/or blade techniques. Inexemplary embodiments, an air atomization device such as an air brush oran automated air/liquid spray can be used for spray coating. In anotherexample, a programmable dispenser can be used to apply the coatingmaterial to conduct a flow coating.

In an embodiment, the sacrificial coating can cover a portion of a majorsurface of the intermediate transfer member. The major outer surface ofthe intermediate transfer member can comprise, for example, silicone ora fluorinated polymer.

It has been found that the sacrificial coating overcomes the wet imagequality problem discussed above by providing an ink wetting surface onthe intermediate transfer member. The coatings may also improve theimage cohesion significantly to enable excellent image transfer.

FIG. 1 illustrates a high-speed aqueous ink image producing machine orprinter 10, according to an embodiment of the present disclosure. Asillustrated, the printer 10 is an indirect printer that forms an inkimage on a surface of a blanket 21 mounted about an intermediaterotating member 12 and then transfers the ink image to media passingthrough a nip 18 formed between the blanket 21 and the transfix roller19. The surface 14 of the blanket 21 is referred to as the imagereceiving surface of the blanket 21 and the rotating member 12 since thesurface 14 receives a sacrificial coating and the aqueous ink imagesthat are transfixed to print media during a printing process. A printcycle is now described with reference to the printer 10. As used in thisdocument, “print cycle” refers to the operations of a printer to preparean imaging surface for printing, ejection of the ink onto the preparedsurface, treatment of the ink on the imaging surface to stabilize andprepare the image for transfer to media, and transfer of the image fromthe imaging surface to the media.

The printer 10 includes a frame 11 that supports directly or indirectlyoperating subsystems and components, which are described below. Theprinter 10 includes an intermediate transfer member, which isillustrated as rotating imaging drum 12 in FIG. 1, but can also beconfigured as a supported endless belt. The imaging drum 12 has an outerblanket 21 mounted about the circumference of the drum 12. The blanketmoves in a direction 16 as the member 12 rotates. A transfix roller 19rotatable in the direction 17 is loaded against the surface of blanket21 to form a transfix nip 18, within which ink images formed on thesurface of blanket 21 are transfixed onto a print medium 49. In someembodiments, a heater in the drum 12 (not shown) or in another locationof the printer heats the image receiving surface 14 on the blanket 21 toa temperature in a range of, for example, approximately 50° C. toapproximately 70° C. The elevated temperature promotes partial drying ofthe liquid carrier that is used to deposit the sacrificial coating andof the water in the aqueous ink drops that are deposited on the imagereceiving surface 14.

The blanket is formed of a material having a relatively low surfaceenergy to facilitate transfer of the ink image from the surface of theblanket 21 to the print medium 49 in the nip 18. Such materials includepolysiloxanes, fluoro-silicones, fluoropolymers such as VITON or TEFLONand the like. A surface maintenance unit (SMU) 92 removes residual inkleft on the surface of the blanket 21 after the ink images aretransferred to the print medium 49. The low energy surface of theblanket does not aid in the formation of good quality ink images becausesuch surfaces do not spread ink drops as well as high energy surfaces.

In an embodiment more clearly depicted in FIG. 2, the SMU 92 includes acoating applicator, such as a donor roller 404, which is partiallysubmerged in a reservoir 408 that holds a sacrificial coatingcomposition. The donor roller 404 rotates in response to the movement ofthe image receiving surface 14 in the process direction. The donorroller 404 draws the liquid sacrificial coating composition from thereservoir 408 and deposits a layer of the composition on the imagereceiving surface 14. As described below, the sacrificial coatingcomposition is deposited as a uniform layer having any desiredthickness. Examples include thicknesses ranging from about 0.1 μm toabout 10 μm. The SMU 92 deposits the sacrificial coating composition onthe image receiving surface 14. After a drying process, the driedsacrificial coating substantially covers the image receiving surface 14before the printer ejects ink drops during a print process. In someillustrative embodiments, the donor roller 404 is an anilox roller or anelastomeric roller made of a material, such as rubber. The SMU 92 can beoperatively connected to a controller 80, described in more detailbelow, to enable the controller to operate the donor roller, as well asa metering blade and a cleaning blade, selectively to deposit anddistribute the coating material onto the surface of the blanket and toremove un-transferred ink and any sacrificial coating residue from thesurface of the blanket 21.

Referring back to FIG. 1, the printer 10 includes a dryer 96 that emitsheat and optionally directs an air flow toward the sacrificial coatingcomposition that is applied to the image receiving surface 14. The dryer96 facilitates the evaporation of at least a portion of the liquidcarrier from the sacrificial coating composition to leave a dried layeron the image receiving surface 14 before the intermediate transfermember passes the printhead modules 34A-34D to receive the aqueousprinted image.

The printer 10 can include an optical sensor 94A, also known as animage-on-drum (“IOD”) sensor, which is configured to detect lightreflected from the blanket surface 14 and the sacrificial coatingapplied to the blanket surface as the member 12 rotates past the sensor.The optical sensor 94A includes a linear array of individual opticaldetectors that are arranged in the cross-process direction across theblanket 21. The optical sensor 94A generates digital image datacorresponding to light that is reflected from the blanket surface 14 andthe sacrificial coating. The optical sensor 94A generates a series ofrows of image data, which are referred to as “scanlines,” as theintermediate transfer member 12 rotates the blanket 21 in the direction16 past the optical sensor 94A. In one embodiment, each optical detectorin the optical sensor 94A further comprises three sensing elements thatare sensitive to wavelengths of light corresponding to red, green, andblue (RGB) reflected light colors. Alternatively, the optical sensor 94Aincludes illumination sources that shine red, green, and blue light or,in another embodiment, the sensor 94A has an illumination source thatshines white light onto the surface of blanket 21 and white lightdetectors are used. The optical sensor 94A shines complementary colorsof light onto the image receiving surface to enable detection ofdifferent ink colors using the photodetectors. The image data generatedby the optical sensor 94A can be analyzed by the controller 80 or otherprocessor in the printer 10 to identify the thickness of the sacrificialcoating on the blanket and the area coverage. The thickness and coveragecan be identified from either specular or diffuse light reflection fromthe blanket surface and/or coating. Other optical sensors, such as 94B,94C, and 94D, are similarly configured and can be located in differentlocations around the blanket 21 to identify and evaluate otherparameters in the printing process, such as missing or inoperativeinkjets and ink image formation prior to image drying (94B), ink imagetreatment for image transfer (94C), and the efficiency of the ink imagetransfer (94D). Alternatively, some embodiments can include an opticalsensor to generate additional data that can be used for evaluation ofthe image quality on the media (94E).

The printer 10 includes an airflow management system 100, whichgenerates and controls a flow of air through the print zone. The airflowmanagement system 100 includes a printhead air supply 104 and aprinthead air return 108. The printhead air supply 104 and return 108are operatively connected to the controller 80 or some other processorin the printer 10 to enable the controller to manage the air flowingthrough the print zone. This regulation of the air flow can be throughthe print zone as a whole or about one or more printhead arrays. Theregulation of the air flow helps prevent evaporated solvents and waterin the ink from condensing on the printhead and helps attenuate heat inthe print zone to reduce the likelihood that ink dries in the inkjets,which can clog the inkjets. The airflow management system 100 can alsoinclude sensors to detect humidity and temperature in the print zone toenable more precise control of the temperature, flow, and humidity ofthe air supply 104 and return 108 to ensure optimum conditions withinthe print zone. Controller 80 or some other processor in the printer 10can also enable control of the system 100 with reference to ink coveragein an image area or even to time the operation of the system 100 so aironly flows through the print zone when an image is not being printed.

The high-speed aqueous ink printer 10 also includes an aqueous inksupply and delivery subsystem 20 that has at least one source 22 of onecolor of aqueous ink. Since the illustrated printer 10 is a multicolorimage producing machine, the ink delivery system 20 includes, forexample, four (4) sources 22, 24, 26, 28, representing four (4)different colors CYMK (cyan, yellow, magenta, black) of aqueous inks. Inthe embodiment of FIG. 1, the printhead system 30 includes a printheadsupport 32, which provides support for a plurality of printhead modules,also known as print box units, 34A through 34D. Each printhead module34A-34D effectively extends across the width of the blanket and ejectsink drops onto the surface 14 of the blanket 21. A printhead module caninclude a single printhead or a plurality of printheads configured in astaggered arrangement. Each printhead module is operatively connected toa frame (not shown) and aligned to eject the ink drops to form an inkimage on the coating on the blanket surface 14. The printhead modules34A-34D can include associated electronics, ink reservoirs, and inkconduits to supply ink to the one or more printheads. In the illustratedembodiment, conduits (not shown) operatively connect the sources 22, 24,26, and 28 to the printhead modules 34A-34D to provide a supply of inkto the one or more printheads in the modules. As is generally familiar,each of the one or more printheads in a printhead module can eject asingle color of ink. In other embodiments, the printheads can beconfigured to eject two or more colors of ink. For example, printheadsin modules 34A and 34B can eject cyan and magenta ink, while printheadsin modules 34C and 34D can eject yellow and black ink. The printheads inthe illustrated modules are arranged in two arrays that are offset, orstaggered, with respect to one another to increase the resolution ofeach color separation printed by a module. Such an arrangement enablesprinting at twice the resolution of a printing system only having asingle array of printheads that eject only one color of ink. Althoughthe printer 10 includes four printhead modules 34A-34D, each of whichhas two arrays of printheads, alternative configurations include adifferent number of printhead modules or arrays within a module.

After the printed image on the blanket surface 14 exits the print zone,the image passes under an image dryer 130. The image dryer 130 includesa heater, such as a radiant infrared, radiant near infrared and/or aforced hot air convection heater 134, a dryer 136, which is illustratedas a heated air source 136, and air returns 138A and 1386. The infraredheater 134 applies infrared heat to the printed image on the surface 14of the blanket 21 to evaporate water or solvent in the ink. The heatedair source 136 directs heated air over the ink to supplement theevaporation of the water or solvent from the ink. In one embodiment, thedryer 136 is a heated air source with the same design as the dryer 96.While the dryer 96 is positioned along the process direction to dry thesacrificial coating, the dryer 136 is positioned along the processdirection after the printhead modules 34A-34D to at least partially drythe aqueous ink on the image receiving surface 14. The air is thencollected and evacuated by air returns 138A and 138B to reduce theinterference of the air flow with other components in the printing area.

As further shown, the printer 10 includes a print medium supply andhandling system 40 that stores, for example, one or more stacks of paperprint mediums of various sizes. The print medium supply and handlingsystem 40, for example, includes sheet or substrate supply sources 42,44, 46, and 48. In the embodiment of printer 10, the supply source 48 isa high capacity paper supply or feeder for storing and supplying imagereceiving substrates in the form of cut print mediums 49, for example.The print medium supply and handling system 40 also includes a substratehandling and transport system 50 that has a media pre-conditionerassembly 52 and a media post-conditioner assembly 54. The printer 10includes an optional fusing device 60 to apply additional heat andpressure to the print medium after the print medium passes through thetransfix nip 18. In the embodiment of FIG. 1, the printer 10 includes anoriginal document feeder 70 that has a document holding tray 72,document sheet feeding and retrieval devices 74, and a document exposureand scanning system 76.

Operation and control of the various subsystems, components andfunctions of the machine or printer 10 are performed with the aid of acontroller or electronic subsystem (ESS) 80. The ESS or controller 80 isoperably connected to the intermediate transfer member 12, the printheadmodules 34A-34D (and thus the printheads), the substrate supply andhandling system 40, the substrate handling and transport system 50, and,in some embodiments, the one or more optical sensors 94A-94E. The ESS orcontroller 80, for example, is a self-contained, dedicated mini-computerhaving a central processor unit (CPU) 82 with electronic storage 84, anda display or user interface (UI) 86. The ESS or controller 80, forexample, includes a sensor input and control circuit 88 as well as apixel placement and control circuit 89. In addition, the CPU 82 reads,captures, prepares and manages the image data flow between image inputsources, such as the scanning system 76, or an online or a work stationconnection 90, and the printhead modules 34A-34D. As such, the ESS orcontroller 80 is the main multi-tasking processor for operating andcontrolling all of the other machine subsystems and functions, includingthe printing process discussed below.

The controller 80 can be implemented with general or specializedprogrammable processors that execute programmed instructions. Theinstructions and data required to perform the programmed functions canbe stored in memory associated with the processors or controllers. Theprocessors, their memories, and interface circuitry configure thecontrollers to perform the operations described below. These componentscan be provided on a printed circuit card or provided as a circuit in anapplication specific integrated circuit (ASIC). Each of the circuits canbe implemented with a separate processor or multiple circuits can beimplemented on the same processor. Alternatively, the circuits can beimplemented with discrete components or circuits provided in very largescale integrated (VLSI) circuits. Also, the circuits described hereincan be implemented with a combination of processors, ASICs, discretecomponents, or VLSI circuits.

Although the printer 10 in FIG. 1 is described as having a blanket 21mounted about an intermediate rotating member 12, other configurationsof an image receiving surface can be used. For example, the intermediaterotating member can have a surface integrated onto its circumferencethat enables an aqueous ink image to be formed on the surface.Alternatively, a blanket is configured as an endless rotating belt forformation of an aqueous image. Other variations of these structures canbe configured for this purpose. As used in this document, the term“intermediate imaging surface” includes these various configurations.

Once an image or images have been formed on the blanket and coatingunder control of the controller 80, the illustrated inkjet printer 10operates components within the printer to perform a process fortransferring and fixing the image or images from the blanket surface 14to media. In the printer 10, the controller 80 operates actuators todrive one or more of the rollers 64 in the media transport system 50 tomove the print medium 49 in the process direction P to a positionadjacent the transfix roller 19 and then through the transfix nip 18between the transfix roller 19 and the blanket 21. The transfix roller19 applies pressure against the back side of the print medium 49 inorder to press the front side of the print medium 49 against the blanket21 and the intermediate transfer member 12. Although the transfix roller19 can also be heated, in the exemplary embodiment of FIG. 1, thetransfix roller 19 is unheated. Instead, the pre-heater assembly 52 forthe print medium 49 is provided in the media path leading to the nip.The pre-conditioner assembly 52 conditions the print medium 49 to apredetermined temperature that aids in the transferring of the image tothe media, thus simplifying the design of the transfix roller. Thepressure produced by the transfix roller 19 on the back side of theheated print medium 49 facilitates the transfixing (transfer and fusing)of the image from the intermediate transfer member 12 onto the printmedium 49. The rotation or rolling of both the intermediate transfermember 12 and transfix roller 19 not only transfixes the images onto theprint medium 49, but also assists in transporting the print medium 49through the nip. The intermediate transfer member 12 continues to rotateto enable the printing process to be repeated.

After the intermediate transfer member moves through the transfix nip18, the image receiving surface passes a cleaning unit that removesresidual portions of the sacrificial coating and small amounts ofresidual ink from the image receiving surface 14. In the printer 10, thecleaning unit is embodied as a cleaning blade 95 that engages the imagereceiving surface 14. The blade 95 is formed from a material that wipesthe image receiving surface 14 without causing damage to the blanket 21.For example, the cleaning blade 95 is formed from a flexible polymermaterial in the printer 10. As depicted below in FIG. 1, anotherembodiment has a cleaning unit that includes a roller or other memberthat applies a mixture of water and detergent to remove residualmaterials from the image receiving surface 14 after the intermediatetransfer member moves through the transfix nip 18. As used herein, theterm “detergent” or cleaning agent refers to any surfactant, solvent, orother chemical compound that is suitable for removing any sacrificialcoating and any residual ink that may remain on the image receivingsurface from the image receiving surface. One example of a suitabledetergent is sodium stearate, which is a compound commonly used in soap.Another example is IPA, which is common solvent that is very effectiveto remove ink residues from the image receiving surface. In anembodiment, no residue of the sacrificial coating layer remains on theITM after transferring the ink and sacrificial layer, in which casecleaning of the ITM to remove residual sacrificial coating may not be anissue.

FIG. 3 depicts a process 700 for operating an aqueous indirect inkjetprinter using a sacrificial coating composition comprising the latex, asdescribed herein, to form a dried coating on an image receiving surfaceof an intermediate transfer member prior to ejecting liquid ink dropsonto the dried layer. In the discussion below, a reference to theprocess 700 performing an action or function refers to a controller,such as the controller 80 in the printer 10, executing stored programmedinstructions to perform the action or function in conjunction with othercomponents of the printer. The process 700 is described in conjunctionwith FIG. 1 showing the printer 10, and FIG. 4A-FIG. 4E showing theblanket and coatings, for illustrative purposes. The sacrificialcoatings and processes of employing these coatings are not limited touse with printer 10, but can potentially be employed with any inkjetprinter comprising an intermediate transfer member, as would be readilyunderstood by one of ordinary skill in the art.

Process 700 begins as the printer applies a layer of a sacrificialcoating composition comprising a liquid carrier to the image receivingsurface of the intermediate transfer member (block 704). In the printer10, the drum 12 and blanket 21 move in the process direction along theindicated circular direction 16 during the process 700 to receive thesacrificial coating composition.

In an embodiment, the liquid carrier is water or another liquid, such asalcohol, which partially evaporates from the image receiving surface andleaves a dried layer on the image receiving surface. In FIG. 4A, thesurface of the intermediate transfer member 504 is covered with thesacrificial coating composition 508. The SMU 92 deposits the sacrificialcoating composition on the image receiving surface 14 of the blanket 21to form a uniform hydrophilic coating. A greater coating thickness ofthe sacrificial coating composition enables formation of a uniform layerthat completely covers the image receiving surface, but the increasedvolume of liquid carrier in the thicker coating requires additionaldrying time or larger dryers to remove the liquid carrier to form adried layer. Thinner coatings of the sacrificial coating compositionrequire the removal of a smaller volume of the liquid carrier to formthe dried layer, but if the sacrificial coating is too thin, then thecoating may not fully cover the image receiving surface. In certainembodiments the sacrificial coating composition with the liquid carrieris applied at a thickness of between approximately 1 μm and 10 μm.Process 700 continues as a dryer in the printer dries the sacrificialcoating composition to remove at least a portion of the liquid carrierand to form a dried layer on the image receiving surface (block 708). Inthe printer 10 the dryer 96 applies radiant heat and optionally includesa fan to circulate air onto the image receiving surface of the drum 12or belt 13. FIG. 4B depicts the dried layer 512. The dryer 96 removes aportion of the liquid carrier, which decreases the thickness of thelayer that is formed on the image receiving surface. In the printer 10the thickness of the dried layer 512 can be any suitable desiredthickness. Example thicknesses range from about 0.1 μm to about 3 μm indifferent embodiments, and in certain specific embodiments from about0.1 to about 0.5 μm.

The dried sacrificial coating 512 is also referred to as a “skin” layer.The dried sacrificial coating 512 has a uniform thickness that coverssubstantially all of the portion of the image receiving surface thatreceives aqueous ink during a printing process. As described above, thedried sacrificial coating 512 covers the image receiving surface ofintermediate transfer member 504. The dried sacrificial coating 512 hasa comparatively high level of adhesion to the image receiving surface ofintermediate transfer member 504, and a comparatively low level ofadhesion to a print medium that contacts the dried layer 512. Asdescribed in more detail below, when aqueous ink drops are ejected ontoportions of the dried layer 512, a portion of the water and othersolvents in the aqueous ink permeates the dried layer 512.

Process 700 continues as the image receiving surface with thehydrophilic skin layer moves past one or more printheads that ejectaqueous ink drops onto the dried sacrificial coating and the imagereceiving surface to form a latent aqueous printed image (block 712).The printhead modules 34A-34D in the printer 10 eject ink drops in theCMYK colors to form the printed image.

The sacrificial coating 512 is substantially impermeable to thecolorants in the ink 524, and the colorants remain on the surface of thedried layer 512 where the aqueous ink spreads. The spread of the liquidink enables neighboring aqueous ink drops to merge together on the imagereceiving surface instead of beading into individual droplets as occursin traditional low-surface energy image receiving surfaces.

Referring again to FIG. 3, the process 700 continues with a partialdrying process of the aqueous ink on the intermediate transfer member(block 716). The drying process removes a portion of the water from theaqueous ink and the sacrificial coating, also referred to as the skinlayer, on the intermediate transfer member so that the amount of waterthat is transferred to a print medium in the printer does not producecockling or other deformations of the print medium. In the printer 10,the heated air source 136 directs heated air toward the image receivingsurface 14 to dry the printed aqueous ink image. In some embodiments,the intermediate transfer member and blanket are heated to an elevatedtemperature to promote evaporation of liquid from the ink. For example,in the printer 10, the imaging drum 12 and blanket 21 are heated to atemperature of 50° C. to 70° C. to enable partial drying of the ink inthe dried layer during the printing process. As depicted in FIG. 4D, thedrying process forms a partially dried aqueous ink 532 that retains areduced amount of water compared to the freshly printed aqueous inkimage of FIG. 4C.

The drying process increases the viscosity of the aqueous ink, whichchanges the consistency of the aqueous ink from a low-viscosity liquidto a higher viscosity tacky material. The drying process also reducesthe thickness of the ink 532. In an embodiment, the drying processremoves sufficient water so that the ink contains less that 5% water orother solvent by weight, such as less than 2% water, or even less than1% water or other solvent, by weight of the ink after the drying processbut prior to transfer to the print medium.

Process 700 continues as the printer transfixes the latent aqueous inkimage from the image receiving surface to a print medium, such as asheet of paper (block 720). In the printer 10, the image receivingsurface 14 of the drum 12 engages the transfix roller 19 to form a nip18. A print medium, such as a sheet of paper, moves through the nipbetween the drum 12 and the transfix roller 19. The pressure in the niptransfers the latent aqueous ink image and a portion of the dried layerto the print medium. After passing through the transfix nip 18, theprint medium carries the printed aqueous ink image. As depicted in FIG.4E, a print medium 536 carries a printed aqueous ink image 532 with thesacrificial coating 512 covering the ink image 532 on the surface of theprint medium 536. The sacrificial coating 512 provides protection to theaqueous ink image from scratches or other physical damage while theaqueous ink image 532 dries on the print medium 536.

During process 700, the printer cleans any residual portions of thesacrificial coating 512 that may remain on the image receiving surfaceafter the transfixing operation (block 724). In one embodiment, a fluidcleaning system 395 uses, for example, a combination of water and adetergent with mechanical agitation on the image receiving surface toremove the residual portions of the sacrificial coating 512 from thesurface of the belt 13. In the printer 10, a cleaning blade 95, whichcan be used in conjunction with water, engages the blanket 21 to removeany residual sacrificial coating 512 from the image receiving surface14. The cleaning blade 95 is, for example, a polymer blade that wipesresidual portions of the sacrificial coating 512 from the blanket 21.

During a printing operation, process 700 returns to the processingdescribed above with reference to block 704 to apply the sacrificialcoating to the image receiving surface, print additional aqueous inkimages, and transfix the aqueous ink images to print media foradditional printed pages in the print process. The illustrativeembodiment of the printer 10 operates in a “single pass” mode that formsthe dried layer, prints the aqueous ink image and transfixes the aqueousink image to a print medium in a single rotation or circuit of theintermediate transfer member. In alternative embodiments, an inkjetemploys a multi-pass configuration where the image receiving surfacecompletes two or more rotations or circuits to form the dried layer andreceive the aqueous ink image prior to transfixing the printed image tothe print medium.

In some embodiments of the process 700, the printer forms printed imagesusing a single layer of ink such as the ink that is depicted in FIG. 4C.In the printer 10, however, the multiple printhead modules enable theprinter to form printed images with multiple colors of ink. In otherembodiments of the process 700, the printer forms images using multipleink colors. In some regions of the printed image, multiple colors of inkmay overlap in the same area on the image receiving surface, formingmultiple ink layers on the sacrificial coating layer. The method stepsin FIG. 3 can be applied to the multiple ink layer circumstance withsimilar results.

The present disclosure is also directed to an imaged final substratemade by the aqueous transfix process described herein. As described indetail above, an ink pattern is formed on the final substrate, which canbe, for example, a paper substrate or any other suitable imagesubstrate. The sacrificial layer comprising the polymer from the latexis transfixed onto the final substrate with the ink pattern to form aprotective film. The protective film can comprise any of the polymersdiscussed herein. For example, the protective film can comprise one ormore repeating polymeric units selected from the group consisting ofacrylate units, n-butyl acrylate units, methacrylate units, methylmethacrylate units, styrene units and butadiene units. The protectivefilm can include any of the other components of the sacrificial layersthat remain solid after final drying, such as the hygroscopic materials,surfactants and optional fillers or additives.

EXAMPLES Example 1: Latex Selection

Table 1A shows two Xerox experimental styrene n-butyl acylate latex,labeled Xerox experimental latex-L and Xerox experimental latex-H, aswell as some commercial latex that were employed in the examples below.These latex were compatible with the selected humectants such asglycerol or sorbitol and formed uniform and stable films on fluorinatedblanket surfaces.

TABLE 1A Various Latex for Sacrificial Coating Application LatexDescription Supplier Tg (° C.) PH Vis (cps) Solid (%) Xerox experimentalXerox 53 1.8 <50 39.9 latex-L Xerox experimental Xerox 82 1.8 <50 42.7latex-H Joncryl 74A BASF −16 8.1 <700 48.5 Joncryl 77 BASF 21 8.3 500 46Resyn 2920 Celanese 12 8.5 <500 45.0 Dur-O-Cryl 69A Celanese 10 3.0 50.045.0

Table 1B shows the ingredients of both Xerox experimental latexcompositions “L” and “H”. An explanation of the acronyms and otheringredient names used in Table 1B are provided below. The latexcompositions can be made using an emulsion polymerization processsimilar to that followed in Example 7, below, except that the amount ofingredients are substituted by those of Table 1B.

-   -   bCEA—beta-carboxyethyl acrylate.    -   ADOD—decane-1,10-diyldiacrylate, which is a long chain        hydrophobic crosslinker.    -   DDT#1, DDT#2—amount of 1-dodecane thiol in Monomer Feed No. 1        and Monomer Feed No. 2, respectively.    -   DOWFAX®—an anionic alkyldiphenyloxide disulfonate surfactant        available from Dow Chemical Company of Midland, Mich.    -   APS—Ammonium persulfate

TABLE 1B Latex Type Xerox Xerox Latex-L Latex-H Styrene (%) 54.0 67.9nBA (%) 34.0 18.6 Methacrylic acid (%) 12.0 13.5 bCEA (pph on St + nBA +MAA) 3.00 3.00 ADOD (pph on St + nBA + MAA) 0.35 0.35 DDT#1 (pph ontotal St + nBA + MAA) 0.620 0.260 DDT#2 (pph on total St + nBA + MAA)2.440 2.130 Dowfax (pph on St + nBA + MAA) 1.00 1.00 APS (pph on St +nBA + MAA) 1.50 1.50 Dowfax partition 15/85 15/85 Seed % 1.0 1.0Particle Size D50 (nm) 100.3 120.1 Particle Size D95 (nm) 141.1 172.4Zeta Potential (mV) ± STD −64.5 ± 15.0 −63.6 ± 10.2 Conductivity (mS/cm)0.129 0.074 pH 1.80 1.83 Solids (%) 39.9 41.9 Mw (k) 43.2 47.4 Mn (k)12.4 13.6 PDI (polydispersity) 3.5 3.5 Tg (° C.) - onset 52.9 81.8 AcidValue (titration) 95.1 50.7 Styrene (ppm) in latex 56 98 nBA (ppm) inlatex 884 14 MAA (ppm) in latex 51 149 % Gel Content 3.8 13.4 Ts(softening point ° C.) 142.3 161.9

Example 2: Sacrificial Coating Compositions Example 2A

Sacrificial coating compositions were prepared with Xerox experimentallatex, as follows.

Example 2A-1

A sacrificial coating solution was prepared by combining and mixing31.25 g Xerox experimental latex-L and 18.75 g glycerol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2A-2

A sacrificial coating solution was prepared by combining and mixing3.251 g Xerox experimental latex-L and 18.75 g sorbitol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2A-3

A sacrificial coating solution was prepared by combining and mixing31.25 g Xerox experimental latex-H and 18.75 g glycerol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2A-4

A sacrificial coating solution was prepared by combining and mixing31.25 g Xerox experimental latex-H and 18.75 g sorbitol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2B

Sacrificial coating compositions were prepared with commerciallyavailable latex, as follows. The loading ratio of polymer solids fromthe latex ranged from about 13 to 15% by weight based on the totalweight of the sacrificial coating composition in examples 2B-1 and 2B-2.

Example 2B-1

A sacrificial coating solution was prepared by combining and mixing31.25 g BASF Joncryl 74A latex and 18.75 g sorbitol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2B-2

A sacrificial coating solution was prepared by combining and mixing31.25 g BASF Joncryl 77 latex and 18.75 g sorbitol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2B-3

A sacrificial coating solution was prepared by combining and mixing31.25 g Celanese Resyn 2920 latex and 18.75 g glycerol into 49.75 g DIwater. Next, 0.25 g Tergitol TMN-6 surfactant was added into the mixtureto make it 100 g of solution.

Example 2B-4

A sacrificial coating solution was prepared by combining and mixing31.25 g Celanese Dur-O-Cryl 69A latex and 18.75 g glycerol into 49.75 gDI water. Next, 0.25 g Tergitol TMN-6 surfactant was added into themixture to make it 100 g of solution.

Example 2B-5

A sacrificial coating solution was prepared by combining and mixing31.25 g Celanese Dur-O-Cryl 69A latex and 18.75 g sorbitol into 49.75 gDI water. Next, 0.25 g Tergitol TMN-6 surfactant was added into themixture to make it 100 g of solution.

Example 3: Optical Microscope Images—Film Forming Property Evaluation

Sacrificial coating solution was coated on blanket substrate using aPamarco anilox roll 165Q13 by hand. The substrate was made fromfluorinated polymer (G621 manufactured by Daikin Industries, Ltd.) and acrosslinker, AO700 (aminoethyl aminopropyl trimethoxysilane fromGelest). The hotplate was setup at 65° C. while the substratetemperature was around 40-50° C. The wet film thickness was around 4-5microns and the dry film thickness was around 200 nm to 2 microns. Thecoated films were dried in oven at 60° C. for 30 seconds.

Example 6: Optical Example 4: Microscope Images—Film Forming PropertyEvaluation

In order to make ink having good wetting and spreading on a sacrificialcoating, it is desirable to achieve a continuous uniform film with thesacrificial coating solution. The optical microscope images were takenon the film which was coated on a substrate made from fluorinatedpolymer (G621 crosslinked with AO700), similar to that of Example 3.

As described above, Example 2A-1 and 2A-2 were prepared using XeroxExperimental latex-L, but with different humectants. Example 2A-1 wasloaded with 18.75% glycerol; Example 2A-2 was loaded with 18.75%sorbitol. Both formulations form a good quality continuous, uniformfilm, as shown in FIG. 5.

Also as described above, Example 2B-1 and Example 2B-2 were preparedusing the same humectant (sorbitol) but with different latex. Bothformulations generated a continuous film, although Joncryl 77demonstrated more uniformity of coating, as shown in FIG. 6.

Example 2B-3 and Example 2B-4, as described above, were prepared usingthe same humectant (glycerol) but with different latex. The surfaceuniformity for both formulations was very similar, as can be seen inFIG. 7.

Example 5: Fibro DAT1100 Ink Drop Evaluation—Ink and Sacrificial CoatingInteraction (Ink Wetting Property)

The ink wettability was characterized by the ink droplet forming on thesacrificial coating. Fibro DAT 1100 was used to capture the inkspreading and contact angles. Lab experimental ink was applied todemonstrate the difference between sacrificial coating formulations. Theink drop size was controlled at 0.5 μl. Since the experimental inkspreading on skin is too fast and the contact angle can't be captured onmost samples, only drop images are demonstrated here.

The group A and B images (FIG. 8) show the comparison of ink droplet ona substrate made from fluorinated polymer (G621 crosslinked with AO700,similar to that of Example 3) without a sacrificial coating as control,and blanket coated with sacrificial solutions comprising Xeroxexperimental latex (example 2A-1, 2A-2, 2A-3 and 2A-4) and commerciallyavailable latex such as Dur-O-Cryl 69A as in examples 2B-1 to 2B-5).Example 2A-1 and Example 2B-4 comprised glycerol as humectant, whileExample 2A-2 and Example 2B-5 comprised sorbitol as humectant. It isclear that both latex compositions loaded with sorbitol provided properink wetting and spreading property while glycerol gave satellitespreading behavior with the loading as high as 18.75%. The ink wettingand spreading properties can also be controlled by the loading level ofhumectant. Lowering the loading level of humectant can effectivelycontrol the interaction between ink and sacrificial coating.

Example 2B-1 and Example 2B-2 comprised the same humectant (sorbitol)but with two different latex compositions. Example 2B-1 comprisesJoncryl 74A and Example 2B-2 comprised Joncryl 77. These twoformulations containing different latex showed much better ink wettingand spreading behavior compared to the no coating control.

Example 6: Air Brush Transfer Test

The same lab experimental ink for contact angle measurement was used fortransfer test. The ink was sprayed on the coated blanket by air brush.The transfer condition was 320° F., 50 psi and 5 seconds dwell time. Theink was transferred from blanket to 120 gsm Digital Color Elite Glosspaper.

The group A images of FIG. 9 show the transfer results. The top image isthe blanket after ink was transferred and the bottom image is the DCEGpaper after ink was transferred. There is no residual ink on blanketcoated with Example 2A-4 solution comprising Xerox experimental latex-Hand sorbitol. There are some residual ink on blanket coated with Example2A-1 and Example 2A-2 comprising Xerox experimental latex-L. Around80-90% ink transferred for these two formulations.

The group B images of FIG. 10 show the transfer on formulation with BASFlatex. The top image is the blanket after transfer and the bottom imageis the DCEG paper after ink transfer. There is no residual ink on theblanket substrate coated with Example 2B-2 solution comprising BASFJoncryl 77 latex and sorbitol. There is some residual ink on blanketcoated with Example 2B-1 solution comprising BASF Joncryl 74A latex andsorbitol.

The group C images of FIG. 11 show the transfer on formulation withCelanese latex. The top image is the blanket after transfer and thebottom image is the DCEG paper after ink transfer. There is almost noresidual ink on blanket coated with Example 2B-4 solution comprisingCelanese Dur-O-Cryl 69A latex and glycerol. There is some residual inkon blanket coated with Example 2B-3 and Example 2B-5.

Example 7: Preparation of an Emulsion Polymerization Latex

A surfactant solution of 1.99 grams of DOWFAX® 2A1 (anionicalkyldiphenyloxide disulfonate) and 285.43 grams of de-ionized water wasprepared by mixing for 10 minutes in a stainless steel holding tank. Theholding tank was then purged with nitrogen for 5 minutes beforetransferring the mixture into a reactor. The reactor was thencontinuously purged with nitrogen while being stirred at 450 RPM. Thereactor was then heated up to 80° C. at a controlled rate. Separately,4.38 grams of ammonium persulfate initiator was dissolved in 45.54 gramsof deionized water.

Separately, a monomer emulsion was prepared by adding 229.13 grams ofstyrene, 62.69 grams of butyl acrylate, 45.39 grams of methacrylic acid,10.12 grams of beta CEA, 2.07 grams of 1-dodecanethiol, and 1.18 gramsof 1,10-decanediol diacrylate (“ADOD”) to a premix of 11.27 grams ofDOWFAX® 2A1 in 152.91 grams of deionized water. 1% of the emulsion (4.3grams) was then slowly added into the reactor containing the aqueoussurfactant phase at 80° C. to form the “seeds” while being purged withnitrogen. The initiator solution was then slowly charged into thereactor. The monomer emulsion was split into two aliquots. The firstaliquot of 252.2 grams of the monomer emulsion (monomer feed no. 1) wasinitially fed into the reactor at 2.03 grams/minute. The second aliquotof 259.8 grams of the monomer emulsion (monomer feed no. 2) was mixedwith 2.45 grams of dichlorodiphenyltrichloroethane (“DDT”) and added tothe reactor at 2.89 grams per minute. Once all of the monomer emulsionwas charged into the reactor, the temperature was held at 80° C. for anadditional two hours to complete the reaction. Full cooling was thenapplied, and the reactor temperature was reduced to 25° C. The productwas collected into a holding tank and sieved with a 25 μm screen. Theparticle size was then measured by a NANOTRAC® U2275E particle sizeanalyzer to have a D50 of 131.3 nm and a D95 of 187.9 nm.

Notwithstanding that the numerical ranges and parameters setting forththe broad scope of the disclosure are approximations, the numericalvalues set forth in the specific examples are reported as precisely aspossible. Any numerical value, however, inherently contains certainerrors necessarily resulting from the standard deviation found in theirrespective testing measurements. Moreover, all ranges disclosed hereinare to be understood to encompass any and all sub-ranges subsumedtherein.

While the present teachings have been illustrated with respect to one ormore implementations, alterations and/or modifications can be made tothe illustrated examples without departing from the spirit and scope ofthe appended claims. In addition, while a particular feature of thepresent teachings may have been disclosed with respect to only one ofseveral implementations, such feature may be combined with one or moreother features of the other implementations as may be desired andadvantageous for any given or particular function. Furthermore, to theextent that the terms “including,” “includes,” “having,” “has,” “with,”or variants thereof are used in either the detailed description and theclaims, such terms are intended to be inclusive in a manner similar tothe term “comprising.” Further, in the discussion and claims herein, theterm “about” indicates that the value listed may be somewhat altered, aslong as the alteration does not result in nonconformance of the processor structure to the illustrated embodiment. Finally, “exemplary”indicates the description is used as an example, rather than implyingthat it is an ideal.

It will be appreciated that variants of the above-disclosed and otherfeatures and functions, or alternatives thereof, may be combined intomany other different systems or applications. Various presentlyunforeseen or unanticipated alternatives, modifications, variations, orimprovements therein may be subsequently made by those skilled in theart which are also intended to be encompasses by the following claims.

What is claimed is:
 1. A sacrificial coating composition for an imagetransfer member in an aqueous ink imaging system, comprising: a latexcomprising polymer particles dispersed in a continuous liquid phase, thelatex comprising a styrene/n-butyl acrylate/methacrylic acid terpolymer;at least one hygroscopic material; at least one surfactant; and water.2. A sacrificial coating composition for an image transfer member in anaqueous ink imaging system, comprising: a latex comprising polymerparticles dispersed in a continuous liquid phase, the polymers in thelatex having a glass transition temperature ranging from about −45° C.to about 100° C., a weight average molecular weight ranging from about3000 to about 300,000, and a particle size ranging from 50 nm to 300 nm;at least one hygroscopic material; at least one surfactant; and water.3. The sacrificial coating composition of claim 2, wherein the polymerparticles comprise one or more repeating polymeric units selected fromthe group consisting of acrylic acid units, acrylate units, methacrylicacid units, methacrylate units, diene units, aliphatic nitrile units,vinyl ether units, vinyl ester units, vinyl ketone units, vinylidenehalide units, vinyl substituted heterocyclic amine units, acrylamideunits, methacrylamide units, vinyl substituted aromatic hydrocarbonunits, vinyl halide units and alkene units.
 4. The sacrificial coatingcomposition of claim 2, wherein the latex comprises one or more acrylicresins made from at least one monomer selected from the group consistingof methyl acrylate, ethyl acrylate, butyl acrylate, methacrylic acid andacrylic acid.
 5. The sacrificial coating composition of claim 2, whereinthe polymer particles comprise polyvinyl acetate copolymer.
 6. Thesacrificial coating composition of claim 2, wherein the hygroscopicmaterial is a polyol.
 7. The sacrificial coating composition of claim 2,wherein the at least one hygroscopic material is selected from the groupconsisting of glycerol, sorbitol, vinyl alcohol, xylitol, maltito,polymeric polyols, glyceryl triacetate, urea and alpha-hydroxy acids(AHA's) or mixtures thereof.
 8. The sacrificial coating composition ofclaim 2, wherein the at least one surfactant is selected from the groupsconsisting of anionic surfactants, nonionic surfactants, siloxanesurfactants and fluorosurfactants.
 9. The sacrificial coatingcomposition of claim 2, wherein the at least one surfactant is non-ionicsurfactant having an HLB value ranging from about 4 to about
 14. 10. Thesacrificial coating composition of claim 2, wherein latex comprises astyrene/n-butyl acrylate/methacrylic acid terpolymer.
 11. A sacrificialcoating composition for an image transfer member in an aqueous inkimaging system, comprising: a latex comprising polymer particlesdispersed in a continuous liquid phase, the latex having a viscosity ofabout 3 cps to about 800 cps at 25° C., a pH ranging from about 3 toabout 10, and a solid content ranging from 5% to about 70%; at least onehygroscopic material; at least one surfactant; and water.
 12. Thesacrificial coating composition of claim 11, wherein latex comprises astyrene/n-butyl acrylate/methacrylic acid terpolymer.
 13. Thesacrificial coating composition of claim 11, wherein the polymerparticles comprise one or more repeating polymeric units selected fromthe group consisting of acrylic acid units, acrylate units, methacrylicacid units, methacrylate units, diene units, aliphatic nitrile units,vinyl ether units, vinyl ester units, vinyl ketone units, vinylidenehalide units, vinyl substituted heterocyclic amine units, acrylamideunits, methacrylamide units, vinyl substituted aromatic hydrocarbonunits, vinyl halide units and alkene units.
 14. The sacrificial coatingcomposition of claim 11, wherein the latex comprises one or more acrylicresins made from at least one monomer selected from the group consistingof methyl acrylate, ethyl acrylate, butyl acrylate, methacrylic acid andacrylic acid.
 15. The sacrificial coating composition of claim 11,wherein the polymers in the latex have a glass transition temperature ofranging from about −45° C. to about 100° C., a weight average molecularweight ranging from about 3000 to about 300,000, and a particle sizeranging from 50 nm to 300 nm.
 16. The sacrificial coating composition ofclaim 11, wherein the polymer particles comprise polyvinyl acetatecopolymer.
 17. The sacrificial coating composition of claim 11, whereinthe hygroscopic material is a polyol.
 18. The sacrificial coatingcomposition of claim 11, wherein the at least one hygroscopic materialis selected from the group consisting of glycerol, sorbitol, vinylalcohol, xylitol, maltito, polymeric polyols, glyceryl triacetate, ureaand alpha-hydroxy acids (AHA's) or mixtures thereof.
 19. The sacrificialcoating composition of claim 11, wherein the at least one surfactant isselected from the groups consisting of anionic surfactants, nonionicsurfactants, siloxane surfactants and fluorosurfactants.
 20. Thesacrificial coating composition of claim 11, wherein the at least onesurfactant is non-ionic surfactant having an HLB value ranging fromabout 4 to about 14.